Windows XP

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Windows XP

• Windows XP is the newer version of Windows NT
• Built on top of a Hardware abstraction layer to
  ensure portability
• Shares some roots with VMS via Dav Cutlet from
  DEC
• Windows XP, XP Pro, Media Center, 64 bit, Tablet
  PC, server etc.
• Windows XP considers Media player, Internet
  Explorer to be part of the OS - legally contested
  as this has implications for the anti-trust
  lawsuits. Typical OS techniques are not
  challenged in courts
• Boots using a BIOS (future generations would use
  EFI)

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Process scheduling

• Threads are scheduling using a priority-based
  preemptive scheduling using a dispatcher
• 32 priority levels
• 1-15 Variable class
• 16-31 Real time
• 32 Dispatcher
• Idle thread is executed if no other thread is
  ready
• Interactive tasks can get upto 3 scheduling
  quantum over time sharing applications

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Virtual memory

• Demand paging with clustering
• On page fault, bring in a cluster of pages
• Each process associated with minimum and maximum
  working set
• Processes at maximum working set will run a local
  page replacement policy
• If less then maximum, then OS will release a free
  page

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File system of choice NTFS

• Directories are implemented using a B tree
• Supports quotas
• Sparse files - if seek() and written, then areas
  that were never written return 0 and not take up
  any space
• Volume mount points - similar to unix mount. NTFS
  does not have to use A, B, etc.
• Directory junction, which is similar to directory
  symbolic links in UNIX
• Hard links to other files in the same volume
• Volume shadow copy to create COW backups of
  recent overwritten versions
• Transparent compession and encryption
• 64 bit clusters for volume size

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Security

• User account based
• Subject used to track user priviledges and
  program access
• All system configuration kept in registry
• Keeps last known safe state to other mechanisms
  to recover from corrupt registry